Prior art of possible relevance includes U.S. Pat. Nos. 1,146,537 issued July 13, 1915 to Tolles; 1,512,152 issued Oct. 21, 1924 to White; 2,453,209 issued Nov. 9, 1948 to Dwight; and 2,702,213 issued Feb. 15, 1955 to Lund.
Tolles discloses a crawler type track assembly utilizing a plurality of track shoes which in turn are mounted on a pair of flexible, endless belts. The belts serve as the means to interconnect the individual shoes to define a continuous assembly.
White discloses a continuous track assembly formed of a plurality of pivotally interconnected links. A roller chain is used to minimize friction between the lower run of the belt and the track frame of the vehicle but otherwise serves no other function.
Dwight provides a continuous track assembly wherein individual track shoes are interconnected by flexible belts in a manner not totally unlike that of Tolles. The flexible belts are elastomeric and reinforced by cable or the like. In addition, Dwight provides two further belts which are not at all attached to the track assembly but which frictionally engage the same along with a drive sprocket to drive the continuous track assembly.
Lund discloses a track assembly including endless bands secured to the individual track shoes in the assembly. Of principal concern to Lund is the provision of a joint which may be utilized to repair the assembly when one of the flexible bands breaks.
None of the foregoing prior art patents consider the problem of slack control in a continuous track assembly. Slack must be provided to allow for the absorption of bumps in uneven ground over which such vehicles typically operate. Slack also is utilized to reduce the magnitude of tension between the drive sprocket and the idler sprocket on the upper run of the belt (hereinafter "slack side tension").
If too much slack is provided, the drive sprocket will jump from one bushing to the next and a positive drive will not be provided. Moreover, scoring of the pins used to interconnect the links is caused by high unit loads where the pins and bushings contact each other. This problem is aggrevated when slack side tension is high.